Sweet Sewage

Artificial sweeteners indicate septic effluent in groundwater

Wastewater from homes contains a cocktail of chemicals that need to be removed or reduced prior to treated water’s release back into the environment. Reliable methods for detecting and quantifying wastewater are needed to study what happens to the chemicals and microbes in wastewater once in the environment to ensure there are no detrimental effects to human or ecosystem health. While certain wastewater chemicals, such as caffeine and pharmaceuticals, have previously been used as indicators of wastewater in lakes, rivers and groundwater, researchers from Environment and Climate Change Canada and the University of Waterloo have been using a different class of wastewater chemicals for this purpose—artificial sweeteners.

Groundwater seeps out of the steep, sandy banks of the southern Nottawasaga River.

Making the Connection

In a study recently published in the Journal of Environmental Quality, groundwater samples were collected from private domestic wells in rural areas of the Nottawasaga River Watershed near Alliston, Ontario, Canada, and from groundwater springs discharging along the banks of the southern Nottawasaga River. More than 30% of the 59 wells analyzed had measureable concentrations of artificial sweeteners, indicating the presence of water that came from the output of a septic system. Results were similar for the groundwater springs, demonstrating that water derived from septic systems travels through the groundwater flow system to discharge points such as the Nottawasaga River. The researchers also calculated that approximately 3.4% to 13.6% of the wells had derived 1% or more of their water from water that previously had been discharged from a septic system.

The four artificial sweeteners measured in the study—acesulfame, saccharin, cyclamate and sucralose—all are approved for human consumption by Health Canada, and therefore their presence in groundwater is, in and of itself, not a human health concern. They do, however, indicate the presence of wastewater and therefore the possibility of other wastewater-derived contaminants, such as pathogens, pharmaceutical and nutrients, which may have health implications for both humans and aquatic organisms. For most aquatic life, the potential effects of artificial sweeteners and their breakdown products are unknown.

Artificial sweeteners are found in a variety of food and beverage products, medicines and even toothpaste. Although they also are used to reduce tooth decay and control diabetes, their main purpose is to reduce caloric intake. The four artificial sweeteners measured in this study are not metabolized in the human body, so they end up in household wastewater. These compounds are subsequently not completely removed by typical wastewater treatment facilities either. In urban areas, household wastewater is collected by sewer networks and treatment is performed by municipal wastewater treatment plants, with the final effluent often discharged to rivers or lakes. In rural areas, private septic systems treat the wastewater prior to discharge to the shallow soil for further treatment; it ultimately ends up in the groundwater system. The concentrations of artificial sweeteners in lakes, rivers and groundwater are typically tens of thousands to hundreds of thousands of times less than a can of diet soda, so these waters would not taste sweetened.

Several factors make artificial sweeteners, particularly acesulfame, excellent tracers of wastewater in the environment. Artificial sweeteners are present at higher concentrations than other organic wastewater compounds that have been used as wastewater tracers (e.g. caffeine, carbamazepine and primidone). Acesulfame also seems to be more resistant to breaking down, and therefore outlasts other wastewater compounds. Additionally, the analytical methods used can detect artificial sweeteners at extremely low concentrations (e.g., 2 ppt for acesulfame) so wastewater can still be detected in the environment long after it has been released and after substantial dilution has occurred.

Research Technician Susan Brown prepares the instrument for the analysis of artificial sweetener concentrations.

Get the Sweet Out

Technologies exist that can remove artificial sweeteners and other organic micropollutants from water and wastewater. For example, Switzerland is enhancing protection of its natural waters by investing 1 billion euros to upgrade approximately 100 of its sewage treatment plants with additional processes, such as ozonation, to remove potentially harmful micropollutants, including pharmaceuticals and personal care products. The widespread incorporation of micropollutant removal technologies into household septic systems is unlikely until these systems are affordable, robust and a government requirement. From a scientific research perspective, tracking artificial sweeteners is a powerful new tool that can be used, not only to detect the presence of wastewater, but also to determine the fate of other wastewater contaminants. Many rivers around the world have been shown to contain high concentrations of artificial sweeteners derived from municipal wastewater treatment plants. Artificial sweeteners also have been used in urban areas to detect areas where sewer pipes are leaking into the groundwater system. As more commercial analytical facilities offer artificial sweetener analysis as a service, it is expected that these compounds will become the preferred method for tracking wastewater in the environment.

Top: Eric Westberg collects a groundwater seep sample along the banks of the southern Nottawasaga River. Bottom: Domestic well water is monitored with a portable water quality meter prior to sampling for chemical analyses.

About the author

John Spoelstra, Ph.D., is an adjunct assistant professor and research scientist for the University of Waterloo. Spoelstra can be reached at [email protected] or 905.336.6246.